Cosmological Redshift

In this session we will,

• Review the principle of cosmological redshift

Before we begin, let’s review. . . . .

The Electromagnetic Spectrum

Redshift

• Light source moving away from you: shifts toward red wavelengths (wavelengths getting bigger)

• Light source moves toward you: shift toward blue wavelengths (wavelengths getting smaller)

Expansion of the Universe

Movie Example

Blueshift?

Measuring Redshift

• Scientists have learned to identify which types of atoms are emitting the light we see from distant galaxies

• They know what wavelength of light each type of atom normally emits

• They measure the wavelength as we actually perceive it and decide if it is shifted to the red or to the blue end of the spectrum (larger or smaller than expected)

Hubble Telescope Images

Questions?